More particularly, the current 4 G communication system evolves into a form of guaranteeing mobility and QoS in a Broadband Wireless Access (BWA) communication system such as a wireless Local Area Network (LAN) system and a wireless Metropolitan Area Network (MAN) system. A representative communication system thereof includes an Institute of Electrical and Electronics Engineers (IEEE)802.16e communication system and a 3rd Generation Partnership Project (3GPP)/3GPP2 Long Term Evolution (LTE) communication system.
This study is approached in an aspect of raising spectral efficiency, and generally, it is widely known that frequency efficiency is maximized when a frequency reuse rate is 1. However, when the frequency reuse rate is 1, the same frequency channel is reused by all base stations, so that a large interference is generated between cells. Since an inter-cell interference becomes large even when each base station raises transmission power under this circumstance, capacity does not increase. Therefore, to raise frequency efficiency, it is important to effectively control the inter-cell interference.
A technique proposed to accomplish this purpose is a Fractional Frequency Reuse (FFR). The FFR can effectively control the inter-cell interference via inter-neighbor base station frequency resource distribution.
FIG. 1 illustrates a frequency allocate pattern of neighbor three sectors in a conventional FFR technique.
Referring to FIG. 1, some (non-segmented partially used sub-carrier (PUSC) zone) 100 of frequency resources are resources all used by three sectors α,β,γ, and are primarily allocated to users located in a cell intermediate region less influenced by the inter-cell interference. The rest (segmented PUSC zone) 110 of the frequency resources are resources used by the three sectors α,β,γ such that they do not overlap, and are primarily allocated to users located in a cell boundary region much influenced by the inter-cell interference. That is, a resource used by one sector in the rest of the resources 110 is not used by neighbor sectors so that interference may not be generated to users located on the cell boundary region who have been allocated a relevant sector. As described above, the FFR technique may improve yield of users of the cell boundary region via SINR improvement.
However, the FFR technique should determine an inter-neighbor sector frequency allocate pattern and a power level in advance when installing a network. Therefore, a frequency allocate pattern and a power level for the FFR should be set suitable for a cell environment when a network is installed. After the network is installed, when the cell environment changes, the frequency allocate pattern and the power level should be manually changed via cell planning.
In addition, in the case where users are concentrated on a cell boundary or a cell intermediate region instantaneously even when a cell environment does not change, an FFR frequency allocate pattern and a power level need to be changed suitable instantaneously. For example, in the case where users are concentrated on a cell intermediate region, since all of the users inside the cell are less influenced by interference, it is optimum to operate an entire frequency resource for a non-segmented PUSC zone. For another example, in the case where all users are located in a cell boundary region, since all of the users inside the cell are much influenced by interference, it is optimum to reduce resources operated for a non-segmented PUSC zone and increase resources operated for a segmented PUSC zone. However, since the conventional FFR technique uses a frequency allocate pattern and power level determined and set in advance, it is impossible to adaptively control the frequency allocate pattern and power level according to an instantaneous user distribution.